Investigation on the effects of SiO2 nanoparticles with different surface affinity on the viscoelasticity of wormlike micelles

The effects of both hydrophilic and hydrophobic SiO2 nanoparticles (NPs) on the viscoelasticity of stearyltrimethylammonium bromide/sodium salicylate wormlike micelles (WLMs) solutions were investigated. The micelle-nanoparticle junctions obviously increased the contour length L-c of the WLMs to facilitate the viscoelasticity of WLMs solution, which could be reflected by cryo-TEM images and Maxwell model. The effects of SiO2 NPs on the zero-shear viscosity and the flow activation energies of WLMs with different surfactant alkyl chain lengths were explored in the controlled experiments. It was found that the viscoelasticity of WLMs/NPs mixture was associated with the strength of the hydrophobic effect between the SiO2 NPs and surfactant molecules in the micelle-nanoparticle junction. The number densities of micelle-nanoparticle junction in hydrophilic and hydrophobic SiO2 NPs systems were calculated by the mathematical model to confirm our proposed hypothesis. (C) 2020 Elsevier B.V. All rights reserved.